1. Field of the Invention
The present invention relates to an immunoassay method and in particular to an immunoassay method for use with lysed whole blood in which antibodies or antigens in a sample are subjected to agglutination reaction with insoluble carriers onto which antigens or antibodies specifically reacting with the antibodies or antigens in the sample have been immobilized. The resulting agglutination mixture is irradiated with near infrared or infrared rays to determine its change in absorbance or its change in scattered light.
2. Description of Related Art
Japanese Patent Publication No. 11575/1983 discloses a prior art method which comprises antigen-antibody reaction between antigen- or antibody-immobilized insoluble carriers and antibodies or antigens in a humor sample, then irradiating the reaction mixture with light with a wavelength of 600 to 2400 nm and measuring the increase in its absorbance. By virtue of its usefulness, this method has become the mainstream of immunoassay method at present as a so-called latex immunoturbidimetry.
However, the measurement sample used in said measurement method is water, serum, urine, saline etc. In addition, matters that require attention in general blood taking for clinical examination are that hemolysis should be avoided to a maximum degree and blood should be separated into serum and plasma as rapidly as possible. The reasons for this include the effect of hemolysis on optical measurement, the incoming and outgoing of substances such as Na, K, Cl through blood membrane, the effect of movement by blood corpuscles metabolism (i.e., transfer of lactic acid and pyruvic acid to serum by glycolysis) and the effect of the difference in concentration of the object component in blood corpuscles and in serum.
For the above reasons, blood obtained from a subject should be a sample separated into serum or plasma by centrifugation. Therefore, such pretreatment by centrifugation may not be carried out in small or private laboratories or urgent laboratories other than central laboratories in large or middle hospitals where a large amount of blood can be dealt with, and therefore the above method is not necessarily universal.
Under the circumstances of such general whole blood handling, in the field of clinical examination there is no accurate and quantitative measurement method in which whole blood can be directly used as a measurement sample without separating it into serum and plasma. Further, the measurement of blood using optical means without hemolysis is inappropriate because of high turbidity caused by erythrocyte.